By late June the grass on the open ground of Thomaston Green comes on thick, and every lawn in town wants cutting twice a week. Peter Overlock Inc. handles the mowing, the trimming in tight around fence posts and granite steps, and the edging that gives a walkway its clean line. Afternoons here have their own particular quality — sun off the harbor end of town, a breeze carrying cut grass three houses down the street. Spring and fall cleanups bracket the season, raking out winter debris in April and clearing leaves before the ground stiffens. A lawn kept on schedule stops being something anyone has to think about, and that is the whole point.